Fluid regulators are commonly used in process control systems to control flow rates and/or pressures of various fluids (e.g., liquids, gases, etc.) through a valve. An instrument (e.g., a controller or a positioner) is often employed to supply control fluid (e.g., air) to the fluid regulator to position a flow control member (e.g., a valve gate, a plug, a closure member, etc.) to regulate the fluid flow through the valve.
Some instruments that supply control fluid to a fluid regulator are coupled to a valve body of the fluid regulator. In some instances, the instrument and the fluid regulator are installed in hazardous locations. In some such instances, a nameplate or label is fixed to the instrument to indicate in which category of hazardous locations the instrument is approved to be installed.